@no_regrets
Yes, I placed the pads under the feet of the turntable, and noticed a significant audible change, but this is largely because I had a Rega P8, which is very sensitive to the surface that it’s sitting on. Try both, and see what you notice. It’s quite fun to experiment with little, inexpensive adjustments to the audio system!
I only tried the rubber ones mainly because they were suitable for the lowest load psi, and designed for small vibrations and designed for acoustic applications. The steel ones have a minimum load of something like 200 psi, as opposed to 2 psi for the rubber ones, and also there isn’t any mention anything about acoustic application or vibrations for the steel ones.